The field of pediatrics in the US began in late-nineteenth century urban slums, where young children were monitored to ensure they received safe milk and mothers were educated about nutrition and hygiene. The subsequent reduction of infectious disease through sanitation and vaccination, and a continuing appreciation of the powerful impact of the social context of children's well being, reinforced this early emphasis on preventive care. The past several decades have seen a shift in the distribution of childhood morbidity, as changing social patterns of family life and access to health care have increased the prevalence of chronic illness and developmental and emotional problems. More recently, practitioners and policymakers have recognized the importance of children's social and physical environments on life-long health and social competence. These changes are casting increasing attention on the preventive care available to young children and their families. Whereas public policies have provided most children with access to health care, questions have been raised about the content and quality of that care. Recommendations to improve the quality of preventive care include such strategies as risk-based individualized care plans; greater use of tested practice management tools, such as flow sheets and e-mail; team care; and standardized data collection, including structured screening. Both the content of preventive care and the training of practitioners to provide that care should be guided by a predetermined set of measurable outcomes for which providers should be held accountable, as well as other outcomes to which they should be expected to contribute.